VI EVOLUTION IN BIOLOGY 191 



Bonnet affirms that, before fecundation, the hen's 

 egg contains an excessively minute but complete 

 chick ; and that fecundation and incubation simply 

 cause this germ to absorb nutritious matters, which 

 are deposited in the interstices of the elementary 

 structures of which the miniature chick, or germ, 

 is made up. The consequence of this intussuscep- 

 tive growth is the " development " or " evolution " 

 of the germ into the visible bird. Thus an organ- 

 ised individual (tout organist] " is a composite body 

 consisting of the original, or elementary, parts and 

 of the matters which have been associated with 

 them by the aid of nutrition ; " so that, if these 

 matters could be extracted from the individual 

 (tout), it would, so to speak, become concentrated 

 in a point, and would thus be restored to its 

 primitive condition of a germ ; "just as by extract- 

 ing from a bone the calcareous substance which is 

 the source of its hardness, it is reduced to its 

 primitive state of gristle or membrane/' l 



"Evolution" and "development" are, for 

 Bonnet, synonymous terms ; and since by " evolu- 

 tion " he means simply the expansion of that 

 which was invisible into visibility, he was natur- 

 ally led to the conclusion, at which Leibnitz had 

 arrived by a different line of reasoning, that no 

 such thing as generation, in the proper sense of 

 the word, exists in Nature. The growth of an 



1 Considerations sur Ics Corps crganises, chap. x. 



